The present invention relates to the art of image display and processing. It finds particular application in an image display/processing device for displaying and morphological processing of sensed images.
Various types of image displays have been developed, including liquid-crystal displays (LCDS) which are electronically switched displays making use of changes in the optical properties of liquid crystals in series with an electric field. A thin film of liquid crystals is sandwiched between glass plates imprinted with transparent electrodes. When a voltage is applied selectively across the electrodes, the liquid crystal molecules between them are rearranged or switched in polarization so that light is either reflected or absorbed in the region bounded by the electrodes to form characters or graphics. Liquid crystals are chemical mixtures that behave like crystals in an electric field.
Glass covers of LCDs are assembled with a predetermined space between them to keep a constant distance. They are then sealed around the edges to contain the viscous liquid crystals, and are equipped with polarizing filters to assist in controlling image output.
Most LCDs today employ twisted-nematic field-effect (TNFE) liquid crystals that provide either dark or black characters on a lighted field. When subjected to an electric field, the TNFE molecules twist changing the optical properties of the light thereby varying reflection or transmittance of the light through the LCD. When the voltage is removed, they recover their normal orientation and are transparent to light. The recovery time is called response time.
In large LCD matrix displays, each pixel is commonly a twisted-nematic cell. Each cell is formed as an x-y coordinate matrix of fine width parallel electrodes formed on the crystal sandwich of the opposing glass plates in a liquid crystal sandwich. These electrodes, are formed by the deposition of a transparent conductive film on the inside of each plate and subsequent photolithographic and etching processes.
The glass plates are assembled so that addressable parallel electrodes are at right angles to each other over the liquid crystal material. A pixel is obtained when the voltage pulses across the opposing electrodes and liquid crystal exceed a predetermined voltage threshold. The LCD is organized so that the rows are pulsed cyclically and the data is multiplexed into the columns synchronously.
Large LCD displays based on metal-insulator-metal (MIM) technology are known. Another active matrix technology is thinfilm, transistor-based (TFT-based) displays. These large-panel liquid-crystal displays use a transistor and capacitor at each pixel location to improve contrast and readability. Conventional LCD pixels are driven only by a short voltage pulse during the scanning cycle but active-matrix pixels are driven by a continuous voltage. The transistor and capacitor hold the pulsed-voltage level indefinitely.
As with image display technology, various types of image processing devices have been developed. One aspect of image processing is the need to electronically acquire the image which is to be processed. Arrays of sensing elements such as photodiode and photoconductors have been found to be suited for such image acquisition.
It is also known that amorphous-silicon and poly-silicon based devices have been developed for a wide variety of applications, including image sensors and flat-panel displays. These devices take advantage of certain amorphous-silicon or poly-silicon film properties, such as low-temperature processing capability, high photoconductivity, high field-effect switching ratio and dopability. Moreover, due to the advent of large-area deposition and photolithographic patterning systems, it is common practice to use large substrates to fabricate these devices to improve productivity and gain cost savings.
This large-area device technology has spawned several page-wide linear-array device applications in the fields of facsimile communication, document scanning, and page printing. Page-wide linear sensors using a Si:H have been used for some time in facsimile applications. For example, a-Si:H arrays of photodiodes individually wirebonded to a number of CMOS LSI chips mounted on the same substrate have been developed.
Commonly, sensor arrays employing photodiodes have the sensors positioned in rows and columns of a x-y coordinate configuration in a manner similar to that of LCD arrangements. Such sensor arrays are also driven in a manner corresponding to that of LCD displays.
The present inventor has noted the similarities existing between 2-D image displays, such as LCDs, and 2-D image sensors, such as photodiode arrays when, for example, large-area amorphous-or poly-silicon electronics are employed. The inventor has determined that the combination of these two technologies allows for very powerful image capture, display, and processing. Therefore, the present invention provides for the combination of these technologies through the integration of a 2-D sensor array with a 2-D image display, whereby with appropriate combination a system is constructed for use as an ordinary flat panel display, and which also is capable of parallel image processing such as morphological processing.